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W1(A),R2(A),W2(A),W2(B),W1(B)

This schedule has WW conflict but not Lost update problem,Please explain why?

Is it possible to have WW conflict without lost update?
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There is a Write-Write conflict because of $W1(A) \rightarrow W2(A)$.

But lost-update problem occurs When same variable is written twice, without any read operation in between.

for example : $W1(A),R2(A),W2(A),W1(A),W1(B)$ has both write-write conflict and lost-update problem.
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Here in the above sequence WW conflict and lost update problem because

                 T1        |        T2                                                   

----------------------------|---------------------------------

          W(A)           |   

----------------------------|---------------------------------

                            |       R(A)

----------------------------|---------------------------------

                            |      W(A)

----------------------------|---------------------------------

                            |      W(B)

----------------------------|---------------------------------     

          W(B)           |   

----------------------------|---------------------------------    

----------------------------|---------------------------------   

Since T1 only writing on A without any read (i.e. Blind Write ) and T1 doesn't perform any operation on A and if the first operation of  T1 on A fails then T2 reads a wrong value of A since T2 reads A before T1 commits so lost update problem.
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W-W and lost update both are same.Actually there is no difference. write-write conflict causes lost-update problem and lost-update problem is only caused by write-write conflict. Just the usage of terminology differs- when we say about the problems in concurrent transactions, we usually say "lost-update" problem. And when we say about the data conflicts which cause problems, we usually say "write-write conflict".  But both are essentially the same

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